Flame-retardant medium-voltage cable resistant to high and low temperatures

Abstract

The invention discloses a flame-retardant medium-voltage cable resistant to high and low temperature, and belongs to the technical field of cable processing, the flame-retardant medium-voltage cable resistant to high and low temperature comprises a plurality of conductors, a polyester tape wrapping layer and an outer sheath layer are sequentially arranged outside the plurality of conductors, and the outer sheath layer is obtained after the polyester tape wrapping layer is coated with a flame-retardant cable material resistant to high and low temperature through melt extrusion and curing molding; the flame-retardant high and low temperature resistant cable material comprises modified polyurethane, modified polysiloxane, a compatilizer, modified aluminum trioxide, an initiator and an additive, the compatilizer is used for promoting crosslinking after fusion of the modified polyurethane, the modified polysiloxane and the modified aluminum trioxide, so that not only are the mechanical strength and the high and low temperature resistance of the medium-voltage cable effectively improved, but also the flame retardant property of the medium-voltage cable is improved.

Description

Technical Field

[0001] The invention relates to the technical field of cable processing, and in particular to a flame-retardant, high- and low-temperature-resistant medium-voltage cable. Background Art

[0002] Medium voltage cable refers to power cables with rated voltage between 1kV and 35kV, which are mainly used for transmission and distribution of medium current or medium voltage levels. Against the background of increasing modern urbanization and large-scale projects, medium voltage cables, as an important carrier of power transmission, have increasingly higher quality and performance requirements.

[0003] The medium voltage cable products in the existing technology, especially the low-smoke halogen-free flame retardant power cables, have certain performance in flame retardancy. However, when the line load is too large, the cable is prone to heat up, resulting in an increase in the temperature of the cable. Unsaturated bonds and easily oxidized groups are easily generated in the sheath material of the cable in a high temperature environment, causing the sheath of the cable to age and become brittle, and even a short circuit may occur in the line, resulting in internal combustion of the wire. Its heat resistance and flame retardant properties need to be further improved. In addition, when the existing medium voltage cable faces a low temperature environment, the sheath of the cable becomes hard, and when bent, the sheath of the cable is prone to cracking, resulting in damage to the cable, and the installation and use cannot meet the requirements of a low temperature environment.

[0004] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0005] The object of the present invention is to provide a flame retardant and high and low temperature resistant medium voltage cable, so as to solve the technical problem in the prior art that the flame retardant and high and low temperature resistant performance of the medium voltage cable needs to be further improved.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A flame-retardant, high-low temperature resistant medium-voltage cable comprises a plurality of conductors, the exteriors of the plurality of conductors being sequentially provided with a polyester tape wrapping layer and an outer sheath layer;

[0008] The outer sheath layer is obtained by melting and extruding a flame-retardant, high and low temperature resistant cable material and coating it on the outside of the polyester tape wrapping layer, and then curing and molding it;

[0009] The flame retardant and high and low temperature resistant cable material comprises the following components in parts by weight: 65-75 parts of modified polyurethane, 35-45 parts of modified polysiloxane, 13-15 parts of compatibilizer, 18-20 parts of modified alumina, 2-3 parts of initiator and 4-6 parts of additive;

[0010] Furthermore, the preparation method of the modified polyurethane is as follows: under the protection of inert gas, [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid, itaconic acid, polytetrahydrofuran ether diol, a catalyst and N,N-dimethylformamide are mixed, the temperature of the reaction system is increased to 70-80°C, isophorone diisocyanate solution is added dropwise to the reaction system, and the reaction is kept warm for 3-5 hours to obtain a polyurethane prepolymer, melamine is added to the polyurethane prepolymer reaction system, and the reaction is kept warm for 2-4 hours, 2-(oxirane-2-yl)ethanol is added to the reaction system, and the reaction is kept warm for 60-80 minutes, and the modified polyurethane is obtained by post-treatment.

[0011] The synthetic reaction formula of modified polyurethane is:

[0012]

[0013]

[0014] Where:

[0015] ;

[0016] ;

[0017]

[0018] The synthetic reaction mechanism of modified polyurethane is:

[0019] During the reaction, the isocyanate groups on the isophorone diisocyanate molecules react with the hydroxyl / carboxyl groups on the [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid, itaconic acid or polytetramethylene glycol molecules to form a condensation reaction. By controlling the molar ratio of isocyanate to hydroxyl+carboxyl groups in the reaction system, an isocyanate-terminated polyurethane prepolymer is prepared. Then, melamine is used as a crosslinking agent, and the isocyanate groups on the polyurethane prepolymer molecular chain react with the amino groups on the crosslinking agent molecules to improve the crosslinking degree of the polyurethane prepolymer. The hydroxyl groups on the 2-(oxirane-2-yl)ethanol molecules react with the isocyanate groups on the polyurethane molecules as the reaction active sites to form epoxy-terminated modifications to prepare modified polyurethane.

[0020] Furthermore, the preparation method of the modified polysiloxane is: trifluoropropylmethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and xylene are mixed, the temperature of the reaction system is increased to 115-125° C., a catalyst is added to the reaction system, the reaction is kept warm for 2.5-3.5 hours, a capping agent is added to the reaction system, the reaction is kept warm for 3-5 hours, and post-processing is performed to obtain the modified polysiloxane.

[0021] The synthetic reaction formula of modified polysiloxane is:

[0022]

[0023] The synthetic reaction mechanism of modified polysiloxane is:

[0024] During the reaction, trifluoropropylmethylcyclotrisiloxane, octamethylcyclotetrasiloxane and 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane molecules are hydrolyzed and ring-opened under the action of high temperature and catalyst, and then condensed to form a long polysiloxane chain modified with trifluoropropyl and unsaturated olefin double bonds. 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane is used as a capping agent. It is hydrolyzed under the action of high temperature and catalyst to form silanol groups, which condense with long polysiloxane chain molecules to form amino-terminated modifications, thereby preparing modified polysiloxane.

[0025] Furthermore, the initiator is dibenzoyl peroxide, and the additives are composed of a dispersant, a lubricant, a plasticizer, and an antioxidant in a weight ratio of 3:2:5:1. The dispersant is a stearate, the lubricant is one or more of butyl stearate, oleamide, and ethylene bisstearamide, the plasticizer is a phthalate, and the antioxidant is any one of antioxidant AW, antioxidant DNP, and antioxidant CPPD.

[0026] Further, the amount ratio of [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid, itaconic acid, polytetramethylene glycol, catalyst and N,N-dimethylformamide is 3g:1g:13g:0.1g:40mL, the catalyst is dibutyltin dilaurate, the isophorone diisocyanate solution is composed of isophorone diisocyanate and N,N-dimethylformamide at a ratio of 1g:2mL, and N in the preparation process of the polyurethane prepolymer is 1g:1g:13g:0.1g:40mL. 异氰酸酯基 :N 羟基+羧基 =1.1:1, the weight ratio of the polytetramethylene ether glycol, melamine and 2-(ethylene oxide-2-yl)ethanol is 10:1:3, and the post-treatment comprises: after the reaction is completed, the temperature of the reaction system is increased to 100° C., and low boiling substances are removed by distillation under reduced pressure to obtain a modified polyurethane.

[0027] Furthermore, the amount ratio of the trifluoropropylmethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and the end-capping agent is 3 mol:4 mol:2 mol:1 mol, the end-capping agent is 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, the amount ratio of the octamethylcyclotetrasiloxane, xylene and the catalyst is 1 g:15 mL:1 g, the catalyst is a 20 wt% formic acid solution, and the post-treatment comprises: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, the pH of the reaction system is adjusted to 7, the liquid is allowed to stand for separation, the organic phase is washed with purified water until neutral and then dried, the organic phase is transferred to a rotary evaporator at a temperature of 95-105° C., and low boiling substances are evaporated under reduced pressure to obtain a modified polysiloxane.

[0028] Furthermore, the preparation method of the compatibilizer is as follows: under the protection of inert gas, polytetramethylene glycol, hydroxy silicone oil, a catalyst and N,N-dimethylformamide are mixed, the temperature of the reaction system is increased to 70-80°C, isophorone diisocyanate solution is added to the reaction system, and the reaction is kept warm for 3-5 hours, 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionamide is added to the reaction system, and the reaction is kept warm for 2-3 hours, and post-processed to obtain the compatibilizer.

[0029] The synthetic reaction formula of the compatibilizer is:

[0030]

[0031]

[0032] Where:

[0033] ;

[0034] .

[0035] The synthetic reaction mechanism of the compatibilizer is:

[0036] During the reaction, the isocyanate group on the isophorone diisocyanate molecule undergoes a condensation reaction with the hydroxyl group on the polytetramethylene ether diol or hydroxy silicone oil molecular chain to prepare a polyurethane molecular chain having isocyanate end-modified polytetramethylene ether diol and hydroxy silicone oil co-blocked, and the isocyanate group on the co-blocked polyurethane molecular chain undergoes a condensation reaction with the amino group on the 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionamide molecule to form ionol end-modified, thereby preparing a compatibilizer.

[0037] Furthermore, the amount ratio of the polytetramethylene glycol, hydroxyl-terminated polysiloxane, catalyst, N,N-dimethylformamide and 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionamide is 5g:4g:0.1g:50mL:1.2g, and the isophorone diisocyanate solution is composed of isophorone diisocyanate and N,N-dimethylformamide at a ratio of 1g:2mL. 异氰酸酯基 :N 羟基 =1.1:1, the post-treatment includes: after the reaction is completed, the temperature of the reaction system is increased to 90-100°C, and low-boiling substances are distilled off under reduced pressure to obtain a compatibilizer.

[0038] Furthermore, the preparation method of modified alumina is: mix nano alumina, anhydrous ethanol, and KH-570, ultrasonically disperse for 30-50 minutes, stir, increase the temperature of the reaction system to 55-65°C, add a catalyst to the reaction system, keep the reaction warm for 60-80 minutes, and post-treat to obtain modified alumina.

[0039] The synthetic reaction formula of modified alumina is:

[0040]

[0041] Where: It is nano-aluminum oxide particles.

[0042] The synthetic reaction mechanism of modified alumina is:

[0043] During the reaction, under the action of the catalyst, the siloxane bonds on the KH-570 molecules are hydrolyzed to form silanol groups, which condense with the active groups on the surface of the nano-alumina particles to form KH-570 coating modifications on the nano-alumina molecules to prepare modified alumina.

[0044] Furthermore, the dosage ratio of the nano-alumina, anhydrous ethanol, KH-570 and catalyst is 5g:50mL:2g:10mL, the catalyst is 0.3-0.5mol / L sodium hydroxide solution, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with purified water until it is neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70°C, and vacuum dried to constant weight to obtain modified alumina.

[0045] The present invention has the following beneficial effects:

[0046] 1. The flame-retardant, high and low temperature resistant medium voltage cable of the present invention is prepared by mixing modified polyurethane and modified polysiloxane, and reinforcing the modified polyurethane and modified polysiloxane with a compatibilizer having a co-blocked segment of polytetramethylene furan ether glycol and hydroxy silicone oil, thereby promoting mutual fusion between the modified polyurethane and modified polysiloxane molecules, and forming bonds between the modified polyurethane and modified polysiloxane molecules through ring-opening condensation of amino groups and epoxy groups, and then promoting cross-linking of the modified polyester, modified polysiloxane and modified alumina with an initiator and high temperature, thereby improving the cross-linking degree between the molecules. , thereby improving the mechanical strength of the medium voltage cable. Modified polyurethane and modified polysiloxane themselves have good high and low temperature resistance. By increasing the intermolecular crosslinking degree of modified polyurethane and modified polysiloxane, it helps to slow down the movement and degradation of the molecular chain during thermal aging, thereby improving the material's resistance to thermal aging and maintaining good mechanical strength in low temperature environments. Nano-alumina in the molecules of the outer sheath layer of the medium voltage cable cooperates with modified polyurethane and modified polysiloxane to form a synergistic flame retardant system, which improves the flame retardant properties of the medium voltage cable.

[0047] 2. The flame-retardant and high-low temperature resistant medium-voltage cable of the present invention is prepared by preparing a large amount of polytetrahydrofuran ether diol-blocked polyurethane prepolymers, the molecular structure of polytetrahydrofuran diol is relatively stable, it is not easy to produce unsaturated bonds and easily oxidized groups under ultraviolet or high temperature environment, and it has good thermal stability. The modified phosphate group on the modified polyurethane molecular chain can enhance the interaction between molecules as a polar functional group, and the phosphate group also has good heat resistance, can improve the cohesive energy and thermal stability of the material, and further improve the heat aging resistance of the polyurethane. The amino group in the melamine molecular structure can further react with the polyurethane prepolymer to form a more compact cross-linked network, which works together with the modified ionol on the compatibilizer molecular chain to improve the high-temperature aging resistance of the medium-voltage cable. The large number of ether bonds contained in the molecular structure of ether diol makes it less likely to become brittle and break in a low temperature environment. The polysiloxane chain itself has good high and low temperature resistance. By introducing trifluoropropyl groups into its molecular chain, the large steric hindrance and strong polarity of the trifluoropropyl side group reduce the electron density around the β carbon atom bonded to the silicon atom, and the β carbon atom is protected by fluorine atoms, thereby blocking the position attacked by oxidation, improving the thermal stability of the modified polysiloxane, and the trifluoropropyl side group also inhibits the crystallization process of the molecular chain, thereby helping to maintain the flexibility of the polysiloxane at low temperatures, further improving the high and low temperature resistance of the modified polysiloxane. After the modified polyurethane and modified siloxane are mixed and dispersed by a compatibilizer, they are bonded under the action of an initiator, further improving their high and low temperature resistance.

[0048] 3. The flame-retardant and high and low temperature resistant medium voltage cable of the present invention introduces phosphoric acid groups and melamine molecules into the modified polyurethane molecular chain. The phosphoric acid groups can decompose at high temperature to produce acidic substances such as phosphoric acid and metaphosphoric acid, promote the formation of a carbon layer on the surface of the polyurethane material, thereby isolating oxygen and heat and achieving a flame retardant effect. Melamine decomposes at high temperature to produce inert gases such as nitrogen and absorbs heat, slows down the combustion rate, and improves the flame retardant properties of the modified polyurethane. The polysiloxane molecules themselves have excellent heat resistance and flame retardancy, and the silicon-oxygen bonds in their molecular chains have high bond energy and are not easily interrupted. In addition, the addition of polysiloxane can further enhance the stability and heat resistance of the carbon layer, so that the carbon layer is not easy to break or fall off at high temperatures, while reducing the amount of smoke and toxic gases generated during the combustion process. Alumina absorbs a large amount of heat during the combustion process, reduces the temperature of the material, slows down the combustion rate, reduces the amount of smoke and toxic gases generated during the combustion process, and forms a physical barrier to prevent the spread of flames and the transfer of heat, further improving the flame retardant properties of the material and the flame retardant properties of the medium voltage cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 It is a schematic structural diagram of the medium voltage cable of the present invention.

[0051] In the figure: 1. Conductor; 2. Polyester tape wrapping layer; 3. Outer sheath layer. DETAILED DESCRIPTION

[0052] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] In the present invention, the molecular weight of polytetramethylene ether glycol is 1000; the viscosity of hydroxy silicone oil is 35mm at 25°C. 2 / s, hydroxyl content is 4%, molecular weight is 800, relative density is 0.95; the polyester tape is PET polyester tape, and the high temperature resistance temperature is 180℃.

[0054] Example 1

[0055] See also Figure 1This embodiment provides a method for preparing a flame-retardant and high and low temperature resistant medium voltage cable, comprising the following steps:

[0056] S1. Preparation of modified polyurethane

[0057] Isophorone diisocyanate and N,N-dimethylformamide were mixed evenly at a ratio of 1 g:2 mL to obtain an isophorone diisocyanate solution for later use;

[0058] Weigh: 60 g of [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid, 20 g of itaconic acid, 260 g of polytetrahydrofuran ether glycol, 2 g of dibutyltin dilaurate and 800 mL of N,N-dimethylformamide into a three-necked flask protected by nitrogen and stir. The temperature of the three-necked flask was raised to 70 °C and heated at N 异氰酸酯基 :N 羟基+羧基 =1.1:1, add the calculated amount of isophorone diisocyanate solution to the three-necked flask, keep warm for 3 hours, add 26g of melamine to the three-necked flask, keep warm for 2 hours, add 78g of 2-(2-oxirane-1)ethanol to the three-necked flask, keep warm for 60 minutes, raise the temperature of the reaction system to 100°C, remove low boiling points under reduced pressure, and obtain modified polyurethane.

[0059] S2. Preparation of modified polysiloxane

[0060] Weigh: 140.6 g of trifluoropropylmethylcyclotrisiloxane, 118.6 g of octamethylcyclotetrasiloxane, 51.7 g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and 1779 mL of xylene, add them into a three-necked flask and stir, the temperature of the three-necked flask is raised to 115°C, 118.6 g of 20 wt% formic acid solution is added into the three-necked flask, and the reaction is kept warm for 2.5 hours, 24.9 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane is added into the three-necked flask, and the reaction is kept warm for 3 hours, the temperature of the three-necked flask is lowered to room temperature, 0.2 mol / L sodium hydroxide solution is added into the three-necked flask, the pH of the reaction solution is adjusted to 7, the liquid is separated by standing, the organic phase is washed with purified water until neutral and then dried, the organic phase is transferred to a rotary evaporator at a temperature of 95°C, and low boiling substances are evaporated under reduced pressure to obtain modified polysiloxane.

[0061] S3. Preparation of compatibilizer

[0062] Isophorone diisocyanate and N,N-dimethylformamide were mixed evenly at a ratio of 1 g:2 mL to obtain an isophorone diisocyanate solution for later use;

[0063] Weigh: 200g of polytetrahydrofuran ether glycol, 160g of hydroxy silicone oil, 4g of catalyst and 2000mL of N,N-dimethylformamide into a three-necked flask protected by nitrogen and stir. The temperature of the three-necked flask is raised to 70°C and heated at N 异氰酸酯基 :N 羟基 =1.1:1 Add the calculated amount of isophorone diisocyanate solution into the three-necked flask, keep warm for 3 hours, add 48g of 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionamide into the three-necked flask, keep warm for 2 hours, raise the temperature of the three-necked flask to 90°C, evaporate low boiling points under reduced pressure to obtain a compatibilizer.

[0064] S4. Preparation of modified aluminum oxide

[0065] Weigh: 50g of nano-alumina, 500mL of anhydrous ethanol, and 20g of KH-570, add them into a three-necked flask, ultrasonically disperse for 30min, fix the three-necked flask on an iron stand with a mechanical stirrer and stir, raise the temperature of the three-necked flask to 55°C, add 100mL of 0.3mol / L sodium hydroxide solution into the three-necked flask, keep warm and react for 60min, lower the temperature of the three-necked flask to room temperature, filter, wash the filter cake with purified water until it is neutral and then drain, transfer the filter cake to a drying oven at a temperature of 60°C, and vacuum dry it to constant weight to obtain modified alumina.

[0066] S5. Preparation of medium voltage cables

[0067] After placing the plurality of conductors 1 in parallel, the plurality of conductors 1 are wound with a polyester tape to form a polyester tape wrapping layer 2 outside the plurality of conductors 1;

[0068] Calcium stearate, butyl stearate, dimethyl phthalate and antioxidant AW are mixed uniformly in a weight ratio of 3:2:5:1 to obtain an additive for later use;

[0069] Weigh by weight: 65 parts of modified polyurethane, 35 parts of modified polysiloxane, 13 parts of compatibilizer, 18 parts of modified alumina, 2 parts of dibenzoyl peroxide and 4 parts of additives are added to a twin-screw extruder. The temperatures of the six temperature zones from the feed end to the discharge end of the twin-screw extruder are 175°C, 180°C, 180°C, 185°C, 185°C and 190°C, respectively. The main shaft speed of the twin-screw extruder is 8r / min. The material is melt-extruded and coated on the outside of the polyester tape coating layer 2 by the twin-screw extruder, cooled and solidified, and an outer sheath layer 3 is formed on the outside of the polyester tape coating layer 2 to obtain a medium voltage cable.

[0070] Example 2

[0071] See also Figure 1 This embodiment provides a method for preparing a flame-retardant and high and low temperature resistant medium voltage cable, comprising the following steps:

[0072] S1. Preparation of modified polyurethane

[0073] Mix isophorone diisocyanate and N,N-dimethylformamide in a ratio of 1 g:2 mL to obtain an isophorone diisocyanate solution for later use;

[0074] Weigh: 60 g of [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid, 20 g of itaconic acid, 260 g of polytetrahydrofuran ether glycol, 2 g of dibutyltin dilaurate and 800 mL of N,N-dimethylformamide into a three-necked flask protected by nitrogen and stir. The temperature of the three-necked flask was raised to 75 °C and heated at N 异氰酸酯基 :N 羟基+羧基 =1.1:1, add the calculated amount of isophorone diisocyanate solution to the three-necked flask, keep warm for 4 hours, add 26g of melamine to the three-necked flask, keep warm for 3 hours, add 78g of 2-(2-oxirane-1)ethanol to the three-necked flask, keep warm for 70 minutes, raise the temperature of the reaction system to 100°C, remove low boiling points under reduced pressure, and obtain modified polyurethane.

[0075] S2. Preparation of modified polysiloxane

[0076] Weigh: 140.6 g of trifluoropropylmethylcyclotrisiloxane, 118.6 g of octamethylcyclotetrasiloxane, 51.7 g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and 1779 mL of xylene, add them into a three-necked flask and stir. Raise the temperature of the three-necked flask to 120°C, add 118.6 g of 20 wt% formic acid solution into the three-necked flask, keep the temperature for reaction for 3.0 h, add 1, 24.9 g of 3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was reacted for 4 hours at a heat preservation temperature. The temperature of the three-necked flask was lowered to room temperature. 0.2 mol / L sodium hydroxide solution was added to the three-necked flask to adjust the pH of the reaction solution to 7. The solution was allowed to stand for separation. The organic phase was washed with purified water until neutral and then dried. The organic phase was transferred to a rotary evaporator at a temperature of 100°C, and low-boiling substances were evaporated under reduced pressure to obtain modified polysiloxane.

[0077] S3. Preparation of compatibilizer

[0078] Mix isophorone diisocyanate and N,N-dimethylformamide in a ratio of 1 g:2 mL to obtain an isophorone diisocyanate solution for later use;

[0079] Weigh: 200g of polytetrahydrofuran ether glycol, 160g of hydroxy silicone oil, 4g of catalyst and 2000mL of N,N-dimethylformamide into a three-necked flask protected by nitrogen and stir. The temperature of the three-necked flask is raised to 75°C and heated at N 异氰酸酯基 :N 羟基=1.1:1 Add the calculated amount of isophorone diisocyanate solution into the three-necked flask, keep warm for 4 hours, add 48g of 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionamide into the three-necked flask, keep warm for 2.5 hours, raise the temperature of the three-necked flask to 95°C, evaporate low boiling points under reduced pressure to obtain a compatibilizer.

[0080] S4. Preparation of modified aluminum oxide

[0081] Weigh: 50g of nano-alumina, 500mL of anhydrous ethanol, and 20g of KH-570, add them into a three-necked flask, ultrasonically disperse for 40min, fix the three-necked flask on an iron stand with a mechanical stirrer and stir, raise the temperature of the three-necked flask to 60°C, add 100mL of 0.4mol / L sodium hydroxide solution into the three-necked flask, keep warm and react for 70min, lower the temperature of the three-necked flask to room temperature, filter, wash the filter cake with purified water until it is neutral and then dry, transfer the filter cake to a drying oven at a temperature of 65°C, and vacuum dry it to constant weight to obtain modified alumina.

[0082] S5. Preparation of medium voltage cables

[0083] After placing the plurality of conductors 1 in parallel, the plurality of conductors 1 are wound with a polyester tape to form a polyester tape wrapping layer 2 outside the plurality of conductors 1;

[0084] Mix zinc stearate, oleamide, diisobutyl phthalate and antioxidant DNP in a weight ratio of 3:2:5:1 to obtain an additive for later use;

[0085] Weigh by weight: 70 parts of modified polyurethane, 40 parts of modified polysiloxane, 14 parts of compatibilizer, 19 parts of modified alumina, 2.5 parts of dibenzoyl peroxide and 5 parts of additives are added to a twin-screw extruder. The temperatures of the six temperature sections from the feed end to the discharge end of the twin-screw extruder are 175°C, 180°C, 180°C, 185°C, 185°C and 190°C, respectively. The main shaft speed of the twin-screw extruder is 9r / min. The material is melt-extruded and coated on the outside of the polyester tape coating layer 2 by the twin-screw extruder, cooled and solidified, and an outer sheath layer 3 is formed on the outside of the polyester tape coating layer 2 to obtain a medium voltage cable.

[0086] Example 3

[0087] See also Figure 1 This embodiment provides a method for preparing a flame-retardant and high and low temperature resistant medium voltage cable, comprising the following steps:

[0088] S1. Preparation of modified polyurethane

[0089] Isophorone diisocyanate and N,N-dimethylformamide were mixed evenly at a ratio of 1 g:2 mL to obtain an isophorone diisocyanate solution for later use;

[0090] Weigh: 60 g of [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid, 20 g of itaconic acid, 260 g of polytetrahydrofuran ether glycol, 2 g of dibutyltin dilaurate and 800 mL of N,N-dimethylformamide into a three-necked flask protected by nitrogen and stir. The temperature of the three-necked flask was raised to 80 °C and heated at N 异氰酸酯基 :N 羟基+羧基 =1.1:1, add the calculated amount of isophorone diisocyanate solution to the three-necked flask, keep warm for 5 hours, add 26g of melamine to the three-necked flask, keep warm for 4 hours, add 78g of 2-(2-oxirane-1)ethanol to the three-necked flask, keep warm for 80 minutes, raise the temperature of the reaction system to 100°C, remove low boiling points under reduced pressure, and obtain modified polyurethane.

[0091] S2. Preparation of modified polysiloxane

[0092] Weigh: 140.6 g of trifluoropropylmethylcyclotrisiloxane, 118.6 g of octamethylcyclotetrasiloxane, 51.7 g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and 1779 mL of xylene, add them into a three-necked flask and stir. Raise the temperature of the three-necked flask to 125°C, add 118.6 g of 20 wt% formic acid solution into the three-necked flask, keep the temperature for reaction for 3.5 h, add 1, 24.9 g of 3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was reacted for 5 hours at a heat preservation temperature. The temperature of the three-necked flask was lowered to room temperature. 0.2 mol / L sodium hydroxide solution was added to the three-necked flask to adjust the pH of the reaction solution to 7. The solution was allowed to stand for separation. The organic phase was washed with purified water until neutral and then dried. The organic phase was transferred to a rotary evaporator at a temperature of 105°C, and low-boiling substances were evaporated under reduced pressure to obtain modified polysiloxane.

[0093] S3. Preparation of compatibilizer

[0094] Isophorone diisocyanate and N,N-dimethylformamide were mixed evenly at a ratio of 1 g:2 mL to obtain an isophorone diisocyanate solution for later use;

[0095] Weigh: 200g of polytetrahydrofuran ether glycol, 160g of hydroxy silicone oil, 4g of catalyst and 2000mL of N,N-dimethylformamide into a three-necked flask protected by nitrogen and stir. The temperature of the three-necked flask is raised to 80℃ and heated at N 异氰酸酯基 :N 羟基=1.1:1 Add the calculated amount of isophorone diisocyanate solution into the three-necked flask, keep warm for 5 hours, add 48g of 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionamide into the three-necked flask, keep warm for 3 hours, raise the temperature of the three-necked flask to 100°C, evaporate low boiling points under reduced pressure to obtain a compatibilizer.

[0096] S4. Preparation of modified aluminum oxide

[0097] Weigh: 50g of nano-alumina, 500mL of anhydrous ethanol, and 20g of KH-570, add them into a three-necked flask, ultrasonically disperse for 50min, fix the three-necked flask on an iron stand with a mechanical stirrer and stir, raise the temperature of the three-necked flask to 65°C, add 100mL of 0.5mol / L sodium hydroxide solution into the three-necked flask, keep warm and react for 80min, lower the temperature of the three-necked flask to room temperature, filter, wash the filter cake with purified water until it is neutral and then drain, transfer the filter cake to a drying oven at a temperature of 70°C, and vacuum dry it to constant weight to obtain modified alumina.

[0098] S5. Preparation of medium voltage cables

[0099] After placing the plurality of conductors 1 in parallel, the plurality of conductors 1 are wound with a polyester tape to form a polyester tape wrapping layer 2 outside the plurality of conductors 1;

[0100] Mix magnesium stearate, ethylene bisstearamide, dibutyl phthalate and antioxidant CPPD in a weight ratio of 3:2:5:1 to obtain an additive for later use;

[0101] Weigh by weight: 75 parts of modified polyurethane, 45 parts of modified polysiloxane, 15 parts of compatibilizer, 20 parts of modified alumina, 3 parts of dibenzoyl peroxide and 6 parts of additives and add them into a twin-screw extruder. The temperatures of the six temperature sections from the feed end to the discharge end of the twin-screw extruder are 175°C, 180°C, 180°C, 185°C, 185°C and 190°C respectively. The main shaft speed of the twin-screw extruder is 10r / min. The material is melt-extruded and coated on the outside of the polyester tape coating layer 2 by the twin-screw extruder, cooled and solidified, and an outer sheath layer 3 is formed on the outside of the polyester tape coating layer 2 to obtain a medium voltage cable.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 3 is that in step S1, [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid is not added.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 3 is that in step S2, trifluoropropylmethylcyclotrisiloxane is not added.

[0106] Comparative Example 3

[0107] The difference between this comparative example and Example 3 is that step S3 is omitted and no compatibilizer is added in step S5.

[0108] Comparative Example 4

[0109] The difference between this comparative example and Example 3 is that the modified alumina in step S5 is replaced by nano alumina in step S4.

[0110] Performance Test:

[0111] The tensile strength, elongation at break, heat aging resistance and low temperature resistance of the medium voltage cable samples prepared in Examples 1-3 and Comparative Examples 1-4 were measured with reference to Standard XF 306.1-2007 "Classification and requirements for flame retardant and fire resistant cables, plastic insulated flame retardant and fire resistant cables, Part 1: Flame retardant cables";

[0112] The specific test results are shown in Table 1 below.

[0113] Table 1-Performance test data of the sample

[0114]

[0115] Data Analysis:

[0116] A comparative analysis of the data in Table 1 above shows that the tensile strength of the medium voltage cable sample prepared by the present invention reaches 17.1 MPa, and the elongation at break reaches 211.5%. After heat aging, the tensile strength reaches 16.2 MPa, the elongation at break reaches 204.0%, the low-temperature tensile elongation reaches 159.5%, the flame retardant grade reaches IA grade, and it has good low-temperature bending performance. All performance test data are better than those of the comparative example, indicating that the present invention not only effectively improves the mechanical strength and high and low temperature resistance of the medium voltage cable, but also improves its flame retardant performance by promoting the cross-linking of modified polyurethane, modified polysiloxane and modified alumina by using a compatibilizer.

[0117] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

[0118] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0119] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flame-retardant, high and low temperature resistant medium voltage cable, comprising a plurality of conductors (1), characterized in that: A polyester tape wrapping layer (2) and an outer sheath layer (3) are sequentially arranged on the outside of the plurality of conductors (1); The outer sheath layer (3) is obtained by melt-extruding a flame-retardant, high-temperature and low-temperature resistant cable material and coating it on the outside of the polyester tape wrapping layer (2), and then curing and molding it; The flame retardant and high and low temperature resistant cable material comprises the following components in parts by weight: 65-75 parts of modified polyurethane, 35-45 parts of modified polysiloxane, 13-15 parts of compatibilizer, 18-20 parts of modified alumina, 2-3 parts of initiator and 4-6 parts of additive, wherein the initiator is dibenzoyl peroxide; the preparation method of the modified polyurethane is: under the protection of inert gas, [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl ] Succinic acid, itaconic acid, polytetramethylene glycol, a catalyst and N,N-dimethylformamide are mixed, the temperature of the reaction system is raised to 70-80°C, isophorone diisocyanate solution is added dropwise to the reaction system, and the reaction is carried out for 3-5 hours to obtain a polyurethane prepolymer, melamine is added to the polyurethane prepolymer reaction system, and the reaction is carried out for 2-4 hours, 2-(oxirane-2-yl)ethanol is added to the reaction system, and the reaction is carried out for 60-80 minutes, and a modified polyurethane is obtained by post-treatment; The preparation method of modified polysiloxane is as follows: trifluoropropylmethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and xylene are mixed, the temperature of the reaction system is increased to 115-125°C, a catalyst is added to the reaction system, the reaction is kept warm for 2.5-3.5 hours, a capping agent is added to the reaction system, the reaction is kept warm for 3-5 hours, and post-processing is performed to obtain modified polysiloxane.

2. A flame-retardant, high and low temperature resistant medium voltage cable according to claim 1, characterized in that: The amount ratio of [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid, itaconic acid, polytetrahydrofuran ether diol, catalyst and N,N-dimethylformamide is 3g:1g:13g:0.1g:40mL, the catalyst is dibutyltin dilaurate, the isophorone diisocyanate solution is composed of isophorone diisocyanate and N,N-dimethylformamide at a ratio of 1g:2mL, and N 异氰酸酯基 :N 羟基+羧基 =1.1:1, the weight ratio of the polytetramethylene ether glycol, melamine and 2-(ethylene oxide-2-yl)ethanol is 10:1:3, and the post-treatment comprises: after the reaction is completed, the temperature of the reaction system is increased to 100° C., and low boiling substances are removed by distillation under reduced pressure to obtain a modified polyurethane.

3. A flame-retardant, high and low temperature resistant medium voltage cable according to claim 1, characterized in that: The amount ratio of trifluoropropylmethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and the end-capping agent is 3 mol:4 mol:2 mol:1 mol, the end-capping agent is 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, the amount ratio of octamethylcyclotetrasiloxane, xylene and the catalyst is 1 g:15 mL:1 g, the catalyst is a 20 wt% formic acid solution, and the post-treatment comprises: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, the pH value of the reaction system is adjusted to 7, the reaction system is allowed to stand for separation, the organic phase is washed with purified water until neutral and then dried, the organic phase is transferred to a rotary evaporator at a temperature of 95-105° C., and low boiling substances are evaporated under reduced pressure to obtain a modified polysiloxane.

4. The flame-retardant and high and low temperature resistant medium voltage cable according to claim 1, characterized in that: The preparation method of the compatibilizer is as follows: under the protection of inert gas, polytetramethylene glycol, hydroxy silicone oil, a catalyst and N,N-dimethylformamide are mixed, the temperature of the reaction system is increased to 70-80°C, isophorone diisocyanate solution is added to the reaction system, and the reaction is kept warm for 3-5 hours, 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionamide is added to the reaction system, and the reaction is kept warm for 2-3 hours, and post-processed to obtain the compatibilizer.

5. A flame-retardant, high and low temperature resistant medium voltage cable according to claim 4, characterized in that: The amount ratio of the polytetramethylene glycol, hydroxyl-terminated polysiloxane, catalyst, N,N-dimethylformamide and 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionamide is 5g:4g:0.1g:50mL:1.2g, and the isophorone diisocyanate solution is composed of isophorone diisocyanate and N,N-dimethylformamide at a ratio of 1g:2mL. 异氰酸酯基 :N 羟基 =1.1:1, the post-treatment includes: after the reaction is completed, the temperature of the reaction system is increased to 90-100°C, and low-boiling substances are distilled off under reduced pressure to obtain a compatibilizer.

6. The flame-retardant and high and low temperature resistant medium voltage cable according to claim 1, characterized in that: The preparation method of modified alumina is as follows: nano alumina, anhydrous ethanol and KH-570 are mixed, ultrasonically dispersed for 30-50 minutes, stirred, the temperature of the reaction system is increased to 55-65°C, a catalyst is added to the reaction system, the reaction is kept warm for 60-80 minutes, and post-processed to obtain modified alumina.

7. A flame-retardant, high and low temperature resistant medium voltage cable according to claim 6, characterized in that: The dosage ratio of the nano-alumina, anhydrous ethanol, KH-570 and catalyst is 5g:50mL:2g:10mL, the catalyst is 0.3-0.5mol / L sodium hydroxide solution, and the post-treatment comprises: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, suction filtration is performed, the filter cake is washed with purified water until it is neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70°C, and vacuum dried to constant weight to obtain modified alumina.

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